1. Technical Field
The present invention relates to a semiconductor device in which a semiconductor element having bumps is mounted on a substrate having electrodes and leads that are connected to the electrodes.
2. Related Art
In semiconductor devices in which a semiconductor element is mounted on a substrate, a method is used in which the semiconductor element is placed on the substrate, after bumps of the semiconductor element are positioned on corresponding electrodes on the substrate, and the substrate and the semiconductor element are fixed by an underfill. The underfill has a function to protect the electrodes and leads of the substrate and the bumps of the semiconductor element from corrosion caused by ambient air or moisture, along with fixing the semiconductor element. The leads are connected to the respective electrodes on the substrate, laid out in a region of the substrate that are covered by the underfill (underfill region), and further led out from the underfill region.
The substrate has a region (overcoat region) covered by an overcoat such that the overcoat region is continuous to or overlaps with the underfill region. Portions of the leads that are outside the underfill region on the substrate are covered by the overcoat in order to protect them from corrosion caused by moisture, or the like.
The leads on the substrate are laid out in various patterns. Heretofore, the patterns described e.g. in JP-A-2004-193223 and JP-A-2005-93468 have been disclosed.
The underfill is dripped, after the semiconductor element is placed on the substrate, along one of the long sides of the semiconductor element, is filled between the substrate and the semiconductor element, and extends such that all the regions between the semiconductor element and the substrate and regions on the substrate adjacent to all sides of the semiconductor element are covered. However, since the semiconductor element is, in general, formed in a rectangular shape and has corner portions, an extension amount of the underfill in regions on the substrate adjacent to the corner portions of the semiconductor element is smaller than an extension amount of the underfill in regions adjacent to the sides of the semiconductor element.
Due to the extension amount of the underfill being small in the regions adjacent to the corner portions, hollows are generated between the underfill region and the overcoat region in these regions, that is regions (hollow regions) on the substrate that are not covered by any of the underfill and the overcoat. As with the layout pattern shown in JP-A-2004-193223, for example, if the leads are led out straight from the underfill region across the nearest long side of the semiconductor element in a plan view, at least a lead that is connected to an electrode on the substrate provided nearest to the corner portion passes through the hollow region, and as a result the lead may suffer from corrosion by moisture or the like.
Thus, as with the lead layout pattern shown in JP-A-2005-93468, a lead layout has been proposed in which the lead connected to an electrode near the corner portion is laid out being bent toward the short side instead of being led out from the long side. However, in this lead layout pattern, since the lead has only one bent portion of a right angle, there is a problem in that the fluidity of the underfill that extends along the bent portion can be reduced, bubbles can be generated in the underfill at the bent portion, and as a result corrosion can occur in the lead caused by moisture or the like penetrated through residues of the bubbles or the bubbles.